Department of Radiation Oncology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Department of Radiation Oncology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Med Dosim. 2022;47(1):e1-e6. doi: 10.1016/j.meddos.2021.09.005. Epub 2021 Oct 23.
Interstitial and intracavitary gynecological HDR brachytherapy involve precise, localized delivery to targets with high dose gradients, sparing adjacent organs at risk (OAR). Due to the proximity of the rectum, bowel and bladder to the target, deviations in the applicator or catheter with respect to patient anatomy can significantly increase dose to OAR. The magnitude and direction of applicator and catheter migration at each fraction was assessed for template interstitial and tandem and ring (T&R) cohorts. The cohort included twelve gynecological patients with intact cervical lesions treated with external beam and brachytherapy. Pre-treatment CT images were registered to the simulation CT with respect to the target. Treatment catheter positions transformed into the planning CT coordinate system to evaluate localized catheter displacement and dose distributions calculated at each fraction. Dose was evaluated on the planning CT with planning contours and dwell locations at treatment position. Absolute deviation, depth and deflection angle for all patients were 4.6 ± 4.2 mm, -1.4 ± 4.0 mm, and 3.1 ± 2.3° respectively (n = 516 catheter positions for all treatment fractions and patients, mean ± SD). Absolute catheter deviation and deflection magnitude for interstitial treatments increased overall with each subsequent fraction with an overall increase of catheter retraction at each fraction (p < 0.005, n = 492 catheters, Kruskal-Wallis). A target EQD2 D90 reduction of 10 ± 10% and 7.7 ± 8.7% of the planned dose for interstitial and T&R cohorts respectively. There was an overall increase in bladder and rectal doses at each fraction. Catheter tracking in interstitial and intracavitary gynecological treatments with CT imaging revealed significant changes in catheter positioning with respect to the target volume. Overall deviations increased in magnitude with each subsequent fraction in the interstitial treatments. This caused patient dosimetry deviations, including target dose reduction and adjacent OAR doses changes.
腔内和间质妇科 HDR 近距离治疗涉及到对靶区的精确、局部高剂量梯度投递，同时保护临近的危险器官（OAR）。由于直肠、肠和膀胱与靶区相邻，施源器或导管相对于患者解剖结构的偏差会显著增加 OAR 的剂量。对模板间质和 tandem and ring（T&R）队列的施源器和导管在每个分次的移动程度和方向进行了评估。该队列包括 12 名接受外照射和近距离治疗的宫颈完整病变的妇科患者。预处理 CT 图像与模拟 CT 配准到靶区。将治疗导管位置转换到规划 CT 坐标系中，以评估每个分次的局部导管位移和剂量分布。在计划 CT 上，根据治疗位置的计划轮廓和驻留点来评估剂量。所有患者的绝对偏差、深度和偏转角分别为 4.6±4.2mm、-1.4±4.0mm 和 3.1±2.3°（所有治疗分次和患者的 516 个导管位置的平均值±标准差）。间质治疗的导管绝对偏差和偏转角随后续分次逐渐增大，每个分次的导管回缩幅度也逐渐增大（p<0.005，n=492 个导管，Kruskal-Wallis）。间质和 T&R 队列的靶区 EQD2 D90 剂量分别减少了 10±10%和 7.7±8.7%。每个分次的膀胱和直肠剂量均有总体增加。CT 成像显示，腔内和间质妇科治疗中的导管跟踪会导致导管相对于靶区体积的位置发生显著变化。间质治疗中，整体偏差随每个分次的进行而逐渐增大。这导致患者剂量学偏差，包括靶区剂量降低和相邻 OAR 剂量变化。
